1. Field of the Invention
This invention relates to imaging apparatus useful, for example, in a double-drum migration imaging copier/duplicator which has a document drum and a transparent drum rotatable about a common axis and driven by a common drive shaft located along such axis. The imaging apparatus of this invention forms an image of a document mounted on the document drum onto the transparent drum without interference from the drive shaft by using only three mirrors and a tilted lens.
2. Description of the Prior Art
It is known to provide a cylindrical drum for carrying a document on the outer surface thereof and to project, by means of a lens and mirrors, an image of a rectangular slit-like portion on that document through an injecting electrode in the form of a transparent cylinder to the outer surface of the electrode cylinder. Then the resulting image is developed by a photoelectrophoretic process. For example, disclosures of such apparatus can be found in U.S. Pat. Nos. 3,628,859, 3,703,335 and 3,730,620. In these patents two separate lens and optical systems are provided, and the document drum and transparent electrode drum are rotated simultaneously by apparatus not located along the axis of rotation of the drums.
The need for two optical systems is expensive and complicated, and it would be desirable to drive both drums from a common drive shaft coaxial with the drums if such could be accomplished without the shaft interferring with principal light rays of the optical system. U.S. Pat. No. 3,609,028 also describes a machine for automatically producing images by means of a photoelectrophoretic process. In this machine a transparent cylindrical electrode receives an image from a mirror located inside the electrode and coaxial with the axis of rotation of the electrode. An image on a film strip is projected onto the mirror and reflected through the electrode. Thus the object drum is eliminated and there is no problem with reflecting light rays through an optical system in a manner which avoids a drive shaft.
U.S. Pat. Nos. 3,052,155 and 3,130,631 disclose driving document and image transport members from common drive means in order to obtain equal linear speeds for the document and an image receiver. However the related imaging apparatus disclosed in such patents can be easily arranged to avoid interference from drive shafts.